How would I go about in making a neck strap?
Model a small section of the strap. Add a curve object. Give the strap an array modifier and a curve deform modifier, set the curve for the curve modifier and set the array to fit curve and select the curve. You can set the start and end caps of the array to get a 'loop' at each end.



Now when you adjust the curve the strap will deform with it. Use &#9096; CtrlT to 'twist' a curve point. For ease of animation you can add a hook to each curve point with &#9096; CtrlH -> Hook to new object. 



For physics you could set a small 'cube' at each curve point as the hook object (or make it the parent to the empty) and set rigid body physics on them.